Reservoirs are used in blood oxygenation apparatus for storing variable amounts of blood during the course of the oxygenation procedure, to facilitate changes in flow rate to the oxygenator and the like.
In the past, the priming volume of prior art reservoirs has been customarily large, since a substantial reservoir volume capacity is frequently needed during oxygenation procedures. However, this is undesirable overall, since a large priming volume in the total oxygenation apparatus requires the use of a large amount of donated blood, with the consequent hazard of disease which may be transmitted through the blood, and of course the increased expense and difficulty in obtaining the blood.
Furthermore, gas bubbles in the blood line introduced through the cardiotomy suction apparatus, if used, and from other sources, are generally vented from a vent at the top of a conventional blood reservoir. Often, during the venting, blood will spatter out of the vent onto the exterior of the oxygenation apparatus, which is, of course, undesirable.
Furthermore, in one type of pediatric surgery, the body temperature of the infant is reduced, followed by an almost complete exsanguination of the blood of the infant into the blood oxygenation system. In this circumstance, there is need for the holding capacity of the reservoir, which is desirably small at the beginning of the operation, to be significantly increased to hold the large amount of blood which is removed from the infant.
Furthermore, it is also important that the blood be retained in sterile, blood-compatible condition, and not to be removed from the system where contamination is possible, but it should be stored within the system until return to the infant a short time later after the radical exsanguination procedure is completed.
In accordance with this invention, a reservoir is provided which exhibits an initial low priming volume, yet which can be easily modified, without opening of the reservoir to the exterior, to provide additional blood holding capacity for the various times during which that is desired. Also, the reservoir of this invention contains an internal chamber separator, which shields the vent of the reservoir from the flow currents of blood passing into and out of the reservoir. This avoids spattering of blood through the vent.
Broman U.S. Pat. No. 2,969,063 discloses a flat chamber in a parenteral solution administration set having narrow portions, which may be closed off with a hemostat to meter selected amounts of parenteral solution to the patient. However, such structure has never been used in conjunction with high-flow, bubble trapping blood reservoirs having multiple entry and exit ports.